The invention relates to novel polyfunctional compounds containing .alpha.-diazo-.beta.-keto ester units and sulfonate units, to a process for their preparation, and to their use as photoactive components in radiation-sensitive mixtures.
Radiation-sensitive mixtures containing photoactive diazo derivatives which are suitable for irradiation with high-energy UV radiation have been described in the literature for some time.
U.S. Pat. No. 4,339,522 discloses positive-working radiation-sensitive mixtures which contain, as a photoactive compound, a diazo derivative of Meldrum's acid. This compound is said to be suitable for exposure to high-energy UV radiation in the range between 200 and 300 nm. On the use of these mixtures, however, it became apparent that the photoactive compound is exuded under the elevated processing temperatures frequently employed in practice; the radiation-sensitive mixture loses its original activity, so that reproducible structuring is not possible.
EP-A 0 198 674 and 0 262 864, JP-A 01/106 034, U.S. Pat. No. 4,622,283 and SU-A 1 004 359 provide 2-diazocyclohexane-1,3-dione or -cyclopentane-1,3-dione derivatives as photoactive compounds for radiation-sensitive mixtures of the type described. These compounds have lower volatility, but this is balanced by the fact that they exhibit, depending on the substitution pattern present, poor compatibility in the radiation-sensitive mixture. This becomes apparent, in particular, on drying of the coatings by the photoactive compound crystallizing out, by their insolubility in solvents which are suitable in practice or by coating inhomogeneity caused by phase separation.
Further positive-working photoactive compounds which are sensitive in the deep UV region are disclosed in EP-A 0 129 694 and U.S. Pat. No. 4,735,885. The compounds described in these documents have the disadvantage that the carbenes formed from these on exposure do not have adequate stability in the matrix for the desired formation of carboxylic acid. This results in an inadequate solubility difference between the exposed and unexposed areas in the developer and thus in an undesirably high removal rate of the unexposed areas. A possible explanation for this phenomenon is given by C.G. Willson et al. in SPIE, Vol. 771, "Advances in Resist Technology and Processing IV", 2 (1987).
EP-A 0 195 986 therefore proposes .alpha.-phosphoryl-substituted diazocarbonyl compounds as photoactive compounds, since these have a higher carbene stability. In practice, however, such compounds will probably not be widely used since atoms of potential use for doping, such as, for example, the phosphorus present in these compounds, must be excluded with extreme care in the processing operations.
H. Sugiyama, K. Ebata, A. Mizushima and K. Nate in their paper "Positive Excimer Laser Resist Prepared with Aliphatic Diazoketones" [SPIE Proc., 920, 51 (1988)], present novel .alpha.-diazoacetoacetates which are employed as photoactive compounds in positive-working radiation-sensitive mixtures, in particular on use of radiation in the deep UV range. Since these are derivatives of acetoacetic acid, the keto group in the .beta.-position to the ester group is directly adjacent to a terminal methyl group.
Diazo derivatives of acetoacetic acid are also employed in EP-A 0 319 325 and DE-A 38 41 571 as radiation-sensitive components in the deep UV range (&lt;300 nm). Radiation-sensitive mixtures which contain the said compounds as photoactive components have good bleaching properties, but their properties with respect to image differentiation are poor.
Aliphatic bis(carbonyl)diazomethanes, which are used in JP-A 01/080 944, have inadequate thermal stability, which is why such compounds are hardly used at all in practice. For bis(carbonyl)diazomethanes, which are claimed in JP-A 63/253 938, 01/106 036 and 01/010 237, the same applies as for the derivatives of acetoacetic acid.